Need Advice on the pH swing from Well Water

[GR33NL3AF]

Here's a diagram which illustrates the point:

Often times stability of products vs reactants can have an effect on the activation energy of a process analogous to that of a catalyst (ie lowering Ea). What you would notice, for instance, is that the activation energy for neutralization would actually be higher in a solution which was saturated with CO2 gas (because the decomposed neutral products would be less favored under these conditions). In a solution with virtually no CO2 the decomposition will take place on the femto->picosecond scale. Because the decomposition is so favored it actually "drags" the rest of the reaction with it.

Some reactions begin with reactants at a lower energy state and progress to a higher energy state, these are not typically spontaneous reactions and they require energy input (like electrolysis of water for instance).

Reactions which go "down" in energy both release energy as a result, and are spontaneous.

Thanks Squiggs! I appreciate you stopping by. However, I am extremely dim witted when it comes to chemistry. Will an R/O system remove all these problems you speak of?

 

[squiggly]

Thanks Squiggs! I appreciate you stopping by. However, I am extremely dim witted when it comes to chemistry. Will an R/O system remove all these problems you speak of?

Well it's not really a "problem," right? It's just the way things are. Not necessarily bad or good, but just a result of what species are present in solution and in what concentrations. Which reactions are favored and which are not.

An RO filter can remove the need for understanding many of these nuances. In terms of home gardening that's precisely what it's meant to do, in fact. It reduces the amount of math you need to do and understanding you need to have about solution chemistry.

It's worth it to really read up about and understand a few topics, though, so that you have a good grasp of what's going on. Including:

pH, concentration/dilutions, solubility, Le Chatlier's Principle (equilibrium), polarity/non-polarity, and dimensional analysis.

For instance let's walk you through solubility just so you can learn HOW to learn about these things without having to go the advanced route.
So the wiki for solubility is here: http://en.wikipedia.org/wiki/Solubility
If you go through that link you'll see a bunch of stuff you can read through quickly. Some you might understand, other stuff you might not (its up to you how deep you want to go to learn the concepts you're missing. If you come across an idea you don't get--google it and see what comes up).

When we get to the math portion of the page your brain probably goes "Shit". But let's just look for a second.

If you look at the pressure dependence of solubility there's a bunch of fancy calculus 3 stuff there--but in the end if you look to the right side of the equation you can see the pressure dependance of solubility is related to the negative of the inverse of temperature. (ie pressure dependence is proportional to -(1/T)).

Likewise if you look to the graphs you can see that the general trend is increasing solubility as temperature increases.

If you look at the henry's law portion under solubility of gasses, you see p = kH * c. Where p is the pressure of gas above solution, c is the concentration in solution and kH is a physical constant specific to that system (CO2 and water for instance).

What this means is that concentration is proportional to 1/kH (you can divide both sides by kH to get this proportionality) what that means is that a larger value for kH will mean a higher concentration of the solute in solution and thus a larger solubility.

So instead of going through and doing all of the algebra and calculus to find the actual numbers you can just think about how these things are related to one another.

Sometimes the math get muddled and can be very confusing (i could show you some math problems that would blow your fucking mind) and then you might need to just walk away--but a lot of it can be shaved down for simplicities sake to these bare bones type arguments.

Also, if you ever had any questions you could come ask yours truly :)

 

[GR33NL3AF]

Well it's not really a "problem," right? It's just the way things are. Not necessarily bad or good, but just a result of what species are present in solution and in what concentrations. Which reactions are favored and which are not.

An RO filter can remove the need for understanding many of these nuances. In terms of home gardening that's precisely what it's meant to do, in fact. It reduces the amount of math you need to do and understanding you need to have about solution chemistry.

It's worth it to really read up about and understand a few topics, though, so that you have a good grasp of what's going on. Including:

pH, concentration/dilutions, solubility, Le Chatlier's Principle (equilibrium), polarity/non-polarity, and dimensional analysis.

For instance let's walk you through solubility just so you can learn HOW to learn about these things without having to go the advanced route.
So the wiki for solubility is here: http://en.wikipedia.org/wiki/Solubility
If you go through that link you'll see a bunch of stuff you can read through quickly. Some you might understand, other stuff you might not (its up to you how deep you want to go to learn the concepts you're missing. If you come across an idea you don't get--google it and see what comes up).

When we get to the math portion of the page your brain probably goes "Shit". But let's just look for a second.

If you look at the pressure dependence of solubility there's a bunch of fancy calculus 3 stuff there--but in the end if you look to the right side of the equation you can see the pressure dependance of solubility is related to the negative of the inverse of temperature. (ie pressure dependence is proportional to -(1/T)).

Likewise if you look to the graphs you can see that the general trend is increasing solubility as temperature increases.

If you look at the henry's law portion under solubility of gasses, you see p = kH * c. Where p is the pressure of gas above solution, c is the concentration in solution and kH is a physical constant specific to that system (CO2 and water for instance).

What this means is that concentration is proportional to 1/kH (you can divide both sides by kH to get this proportionality) what that means is that a larger value for kH will mean a higher concentration of the solute in solution and thus a larger solubility.

So instead of going through and doing all of the algebra and calculus to find the actual numbers you can just think about how these things are related to one another.

Sometimes the math get muddled and can be very confusing (i could show you some math problems that would blow your fucking mind) and then you might need to just walk away--but a lot of it can be shaved down for simplicities sake to these bare bones type arguments.

Also, if you ever had any questions you could come ask yours truly :)

What would we do without you Squiggs????

I really appreciate the time and energy you put into helping me understand. I have jack shit to do for the next 3-4 hours so I'm going to look into it.

Thanks again buddy,

GL

 

[GR33NL3AF]

Well I checked on my experiment and I fudged up...
Because I ran pumps instead of airstones in my 5 gallon buckets the temps were in the mid/high 80's. pH wasn't what I expected though, 6.3-6.4. This is after they had sat for 48 hours.

 

[Seamaiden]

Squiggy, I read that, but I don't understand it.

Green, that suggests something interesting, doesn't it? You mentioned your pumps were *in* the enriched room, yeah? What's interesting to me is that air pump vs water pump shouldn't have made a huge difference in CO2 affecting pH assuming the same saturation levels are achieved using water vs air pumps.

 

[obsoul33t]

thanks squig ..
the problem i have found with high alkalinity is that over time your media's ph will rise and the problem with ro is there is no buffering so the media's ph can wander where it pleases unless you understand how to control media ph through the use of different nitrogen sources ..
i have found that having some alkalinity in your water will stabilize the medias ph ..

now at one of my spots i have alkalinity of 222 mg/l and hc03 at 271 mg/l . my question to squiggly , what would be the ideal way to deal with this high alkalinity sans using an ro filter .
A . use citric acid to bring the water source down to 4.5ph to neutralize all the alkalinity and then add back some calcium carbonate to bring the alkalinity up to between 20-50mg/l then add fertilizer and then readjust ph back up . seems like being that ferts are acidic it would take a bunch of ph up to get in range .. what could be used for ph up that would not change the nkp values ?

B. add fertilizer then ph with citric acid down to proper ph ... seems the alkalinity is still too high doing it this way

C. cut tap with ro until desired alkalinity is reached in my case 30% tap 70% ro ... really don't want to use ro

D. something i have not even thought of yet lol

 

[squiggly]

thanks squig ..
the problem i have found with high alkalinity is that over time your media's ph will rise and the problem with ro is there is no buffering so the media's ph can wander where it pleases unless you understand how to control media ph through the use of different nitrogen sources ..
i have found that having some alkalinity in your water will stabilize the medias ph ..

now at one of my spots i have alkalinity of 222 mg/l and hc03 at 271 mg/l . my question to squiggly , what would be the ideal way to deal with this high alkalinity sans using an ro filter .
A . use citric acid to bring the water source down to 4.5ph to neutralize all the alkalinity and then add back some calcium carbonate to bring the alkalinity up to between 20-50mg/l then add fertilizer and then readjust ph back up . seems like being that ferts are acidic it would take a bunch of ph up to get in range .. what could be used for ph up that would not change the nkp values ?

B. add fertilizer then ph with citric acid down to proper ph ... seems the alkalinity is still too high doing it this way

C. cut tap with ro until desired alkalinity is reached in my case 30% tap 70% ro ... really don't want to use ro

D. something i have not even thought of yet lol

We have to be careful talking about alkalinity. Alkalinity is the measure of the total number of species in solution which can abstract a proton from solution at a given pH. In this way, even citric acid (which is a weak acid) ultimately adds to total alkalinity of a solution--albeit it does so at a much lower pH.

So the idea is that while pH and alkalinity are related, the relation is more about which species have already exhausted their ability to abstract protons at a given pH versus ones which have not.

There are special cases like bicarbonate where the methodology you give in A would work. This is possible because bicarbonate, when converted to carbonic acid via neutralization, rapidly decomposes to H2O and CO2. This allows the species itself to be destroyed by the neutralization.

This is NOT always, or even usually, the case for weak acids and bases. A lot of them stick around even after accepting/donating protons--especially carboxylic acids. Whether or not they are protonated is a function of the pH. So lowering the pH would ultimately just put more citric acid/citrate in the solution if you're dealing with species like this.

You could try an anion exchange resin--but I don't know how cost effective that would be versus just using the RO. I've no experience with scaling these systems up.

You could definitely purify by electrophoresis but I'm positive that's more cost prohibitive and overly technical lol.

You might also try simple activated carbon filtration. It should reduce your alkalinity some, as it preferentially adsorbs anions (there are partial positive charges along the surface of the carbon).

A big problem I've seen a lot of people run into is the presence of buffered systems in their tap water. I think identifying these systems is a huge part of optimizing your water. Do you have a water analysis I can look over for you?

 

[Seamaiden]

Squigs, you just hit on the one... feature? issue with alkalinity that I've had a really hard time wrapping my skull around, and that's how it would not be related to pH; i.e. low pH, yet very resistant to shift, in the aquatic scenario. Even though I was taught to think of alkalinity as resistance to pH shift, in practice for me it's always been tied to carbonates, bicarbonates and subsequent high pH ranges. I'm going to have to reread your post a few times, and even then I'm not sure I'll get it, but thanks for posting it anyway. :)

 

[obsoul33t]

this is a basic ag panel of the well water
carbonate as c03 0 mg/l
bicarbonate as HC03 271 mg/l
hydroxide as OH 0 mg/l
alkalinity 222 mg/l

boron 0
calcium 67.4 mg/l
chloride 31.9 mg/l
magnesium 15.1 mg/l
sodium 17.7 mg/l
sulphate 23.3 mg/l

PH 8.0

when i check the water with my bluelab combo meter it shows 6.8 ph and 0.3EC

thanks for the help Squig

 

[GR33NL3AF]

JUST from the filtration you mentioned? If so, sweet, I envy you because I hate the waste generated using RO. By the same token, that also means that said water of yours has zero alkalinity, which means it has zero resistance to pH shift.

Btw, O2 drives pH up, and CO2 drives it down, in a water column. Freshwater planted tank enthusiasts use CO2 dosing to keep the water pH in their aquaria driven downward.

Hey Sea,
I did a little test with my tap, which comes in around 7.5.

I filled my res (20gal) and with a starting pH of 7.5 I dropped it to 5.5 with citric acid. In this res I have 3 airstones and a water pump for circulation. Next day I checked, back up to 7.4, I dropped it again down to 5.5. Next day same thing, however I removed my air stones, left the pump, and dropped the pH back down to 5.5. Checked it this morning and it only raised to 6.3. This room does not have a CO2 burner just an intake. Is this definitive proof that my air stones were driving the pH up?? Or was adding the pH down a third time, ironically, the right amount.

 

[GR33NL3AF]

this is a basic ag panel of the well water
carbonate as c03 0 mg/l
bicarbonate as HC03 271 mg/l
hydroxide as OH 0 mg/l
alkalinity 222 mg/l

boron 0
calcium 67.4 mg/l
chloride 31.9 mg/l
magnesium 15.1 mg/l
sodium 17.7 mg/l
sulphate 23.3 mg/l

PH 8.0

when i check the water with my bluelab combo meter it shows 6.8 ph and 0.3EC

thanks for the help Squig

No softner? Does your pH change throughout the year? The rain impacts my readings big time.

 

[obsoul33t]

the ph has been consistent throughout the year .. probably due to well depth of 975'

 

[Seamaiden]

Holy SHIT! I thought our well was deep @800'! However, my well readings rarely change, either.

Hey Sea,
I did a little test with my tap, which comes in around 7.5.

I filled my res (20gal) and with a starting pH of 7.5 I dropped it to 5.5 with citric acid. In this res I have 3 airstones and a water pump for circulation. Next day I checked, back up to 7.4, I dropped it again down to 5.5. Next day same thing, however I removed my air stones, left the pump, and dropped the pH back down to 5.5. Checked it this morning and it only raised to 6.3. This room does not have a CO2 burner just an intake. Is this definitive proof that my air stones were driving the pH up?? Or was adding the pH down a third time, ironically, the right amount.

I think it's a combination of both. I believe that if you had dropped it into the 4 range, you might have seen the bounce (all those ions or whatever being 'used up'), but ending up at a lower, more acceptable range. However, neither were you pumping air through the water column and thus, neither were you keeping it at its top saturation for O2.

 

[squiggly]

this is a basic ag panel of the well water
carbonate as c03 0 mg/l
bicarbonate as HC03 271 mg/l
hydroxide as OH 0 mg/l
alkalinity 222 mg/l

boron 0
calcium 67.4 mg/l
chloride 31.9 mg/l
magnesium 15.1 mg/l
sodium 17.7 mg/l
sulphate 23.3 mg/l

PH 8.0

when i check the water with my bluelab combo meter it shows 6.8 ph and 0.3EC

thanks for the help Squig

Okay those numbers agree fairly well with one another.

So think of what I just said earlier. The alkalinity is related to the amount of acid neutralizing base species in solution at that pH.

In your analysis of bicarbonate here 271 mg/L are reported. As I said bicarbonate is a special case where the carbonic acid formed by neutralization turns out to be very unstable and can be destroyed.

Also from your analysis we see total alkalinity is 222 mg/L. The EC measurement also agrees generally with both of these values observed.

What this likely means is that the other solution components (sodium, chloride, calcium, etc.) all slightly confound the measurement of alkalinity (all of these measurements would've been taken at least in triplicate).

In reality your total alkalinity is probably closer to the 271 figure from bicarbonate, because it appears to be entirely made up of bicarbonate (does the analysis report values for %RSD or any other error measurements?).

That the alkalinity came out lower than this figure, though, is a good thing. It means there probably aren't other bases hanging out. So for this situation you CAN go ahead and take the pH of the water very low to remmove the bicarbonate. Bicarbonate has a pKb of about 3.7 which means at ph=3.7 about half of the species in solution will be protonated (on their way to decomposition) and half will be deprotonated.

Getting down to 2.7pH should be good enough to get rid of all traces of bicarbonate. I'd recommend bubbling air through the solution as you're doing this (to remove excess CO2 created by the reaction--thus speeding the decomposition along).

Now if you want to go the extra step, you can do this whole process and then send your water sample (after you pH where you want it) out for analysis to make sure you've done what you set out to do.

I know this will work in a smaller vessel, I can't speak to scaling it up (I'm not a chemical engineer). I'm pretty sure it would work though.

My question, and the reason I'd want to see the post-treatment analysis, is how much shit you'd have to add to solution to get rid of the tiny bit you don't want.

NP broseph, a friend of Alien is a friend of mine--shoot a message to the inbox any time you think I can help--they come right to my phone.